﻿#region 程序集引用
using System;
using System.Collections.Generic;
using System.Text;
#endregion

#region 版权注释
/*===========================================================================
// Copyright (C) 2017 Zhang.cn，并保留所有 
// 作者：李祖武 QQ:6630641
// 创建日期：2018-04-29
// 功能描述： 地图2点距离
===========================================================================*/
#endregion

namespace Zhang.Utils
{
    /// <summary>
    /// 取得2点距离
    /// </summary>
    public class MapDistance
    {
        /// <summary>
        /// 地图中计算距离
        /// </summary>
        /// <param name="lat1"></param>
        /// <param name="lng1"></param>
        /// <param name="lat2"></param>
        /// <param name="lng2"></param>
        /// <returns></returns>
        public static double GetDistance(double lat1, double lng1, double lat2, double lng2)
        {
            double EARTH_RADIUS = 6378.137;
            double radLat1 = rad(lat1);
            double radLat2 = rad(lat2);
            double a = radLat1 - radLat2;
            double b = rad(lng1) - rad(lng2);
            double s = 2 * Math.Asin(Math.Sqrt(Math.Pow(Math.Sin(a / 2), 2) +
             Math.Cos(radLat1) * Math.Cos(radLat2) * Math.Pow(Math.Sin(b / 2), 2)));
            s = s * EARTH_RADIUS;
            s = Math.Round(s * 10000) / 10000;
            return s;
        }

        private static double rad(double d)
        {
            return d * Math.PI / 180.0;
        }
    }
}
